The present invention relates to an absorbent article, and more particularly, an incontinence article, which holds a substantial volume of fluid and has a retainable shape.
Adult diapers are now commercially available with capacities to hold as much as 1,200 ml of fluid. Important advances have also been made in the fit, comfort, closure, quietness, and rewet (surface dryness) of diapers. In spite of these advances, diapers designed for adult incontinence still present problems to users, particularly those who are ambulatory. For example, the fluffy absorbent component, e.g., cellulose pulp fibers, tends to shift and form uneven distributions and clumps. Due to the size and bulkiness of these diapers, wearers tend to be hot, uncomfortable, and concerned about the diaper showing through their garments.
In addition, when away from home, the disposal of diapers presents a problem. Similarly, transporting and storing extra diapers may be an inconvenience.
It is therefore not surprising that there is interest in developing smaller, thinner, more compact articles, e.g., those that can be adhesively attached to undergarments as with sanitary napkins.
Hydrogel forming polymers are of interest in this development, in part, possibly due to the polymers' capacity to absorb 25-35 times their weight in fluid (at least twice the rate of pulp fiber). These polymers, combined in granular form with cellulose pulp structures, are of interest in providing essential technology to achieve sufficient volume capacity in the down-scaling of the size and weight of absorbent articles. Such hydrogel forming polymers are described in detail in Brandt et al, U.S. Pat. No. Re. 32,649. They are often referred to as superabsorbent polymers (SAP).
There are several well known processes for incorporating these hydrogel forming particles into an absorbent material:
1) Direct dry mixing with airborne cellulose pulp in, e.g. fluff forming chambers. PA1 2) Direct application to the surface of various nonwoven fibrous materials or paper. PA1 3) Bonding of SAP granules between two layers of nonwoven material or paper. PA1 4) In-line application of SAP concomitantly with a latex used to bind nonwoven fibers as for example in Makoui, U.S. Pat. No. 5,128,082.
A second challenge in the design of a relatively small, thin, and compact adult incontinence article is the need to rapidly capture and absorb fluid. Pads having absorbent cores which are a combination of a fluid pervious material, cellulose pulp fluff, SAP, and a binder covered with a thin lightweight cover sheet, such as a thermally bonded web of polypropylene staple fibers and backed with an impervious film at 1-3 mil. thickness having an overall length of about 9-10 inches and an overall width of 4-5 inches do not always provide adequate protection, e.g., when the entire bladder is voided since an appreciable quantity of fluid may tend to run off the sides. Such absorbent articles do not provide sufficient drainage, especially in the Z-direction of the device to quickly capture fluids.
In the control of fluids using relatively small, thin, compact articles, a third element of performance is related to the distribution of fluid among the various layers of material which form the overall product. This property contributes importantly to the user's feeling of comfort, dryness, and overall security. More specifically, it is highly desirable that a pad be designed to contain and hold fluids well within the absorbent core even when subjected to the weight of the user.